The SI-111-PW, manufactured by Apogee, is a version of our SI-111 that is fitted with a connector for attachment to a prewired enclosure. This precision infrared radiometer determines the surface temperature of an object without physical contact. The SI-111-PW measures both the subject's surface temperature and the sensor-body temperature. A Campbell Scientific datalogger uses these measurements to calculate the correct temperature of the subject.Read More
The SI-111-PW consists of a thermopile, which measures surface temperature, and a thermistor, which measures sensor body temperature. The two temperature sensors are housed in a rugged aluminum body that contains a germanium window.
Both the thermopile and the thermistor output a millivolt signal that most of our dataloggers can measure. The datalogger uses the Stefan-Boltzman equation to correct for the effect of sensor body temperature on the target temperature. The corrected readings yield an absolute accuracy of ±0.2°C from -10° to 65°C.
Field of View (FOV)
The SI-111-PW has a 22 degree half angle field of view (FOV). The FOV is reported as the half-angle of the apex of the cone formed by the target (cone base) and the detector (cone apex). The target is a circle from which 98% of the radiation viewed by the detector is being emitted; see image.
|Input Power||2.5 V excitation (for thermistor)|
|Response Time||< 1 s (to changes in target temperature)|
|Target Temperature Output Signal||60 μV per °C difference from sensor body|
|Body Temperature Output Signal||0 to 2500 mV|
|Wavelength Range||8 to 14 μm (corresponds to atmospheric window)|
|Field of View (FOV)||22° half angle|
|Operating Temperature Range||-55° to +80°C|
|Operating Relative Humidity Range||0 to 100% RH|
|Cable Description||4.5 m (15 ft) twisted, shielded 4-conductor wire with Santoprene casing, ending in pigtails|
|Diameter||2.3 cm (0.9 in.)|
|Length||6 cm (2.4 in.)|
|Weight||190 g (6.7 oz)|
The SI-111-PQ is often mounted to a CM202, CM204, or CM206 crossarm, a tripod or tower mast, or a user-supplied pole via a CM220 Right Angle Mount or CM230 Adjustable Inclination Mount. The SI-111-PW should be mounted perpendicular to the target surface. Therefore, the CM230 mount is recommended when the target surface is on an incline. The SI-111-PW may also be mounted directly to a user-supplied camera tripod.
The cable on the SI-111-PW is fitted with a connector that attaches to a prewired enclosure.
Number of FAQs related to SI-111-PW: 7
Expand AllCollapse All
The window in the Apogee infrared sensor is inset and protected, but it can become partially blocked in three ways:
Clean the inner threads and sensor window using a cotton swab dipped in the appropriate solvent. For additional cleaning information, see the Maintenance section of the instruction manual.
As a general recommendation, recalibration should be done every two years.
There are two accuracy specifications listed for the SI-111:
Using a radiation shield with the sensor helps keep the sensor body temperature in close approximation to the ambient air temperature. Ultimately, the need to protect the sensor from short-wave radiation is dependent on what is being measured and under what conditions. For example, Campbell Scientific recommends using a radiation shield for canopy measurements.
The SI-111 has been successfully calibrated with a maximum cable length of 100 m without a loss in accuracy. Ideally, the sensor is calibrated with the overall cable length already configured. Our tests have shown, however, that adding a few meters of cable in the field has a negligible effect on the calibration, provided the measurement device has significantly high input impedance, such as with the CR1000.
The SI-111 can be used to measure a wide variety of surfaces, including water and snow. When measuring objects with low emissivity, however, it is particularly important to apply corrections to the measurement.
The information included on a calibration sheet differs with each sensor. For some sensors, the sheet contains coefficients necessary to program a datalogger. For other sensors, the calibration sheet is a pass/fail report.
This depends on the information contained in the calibration sheet: